The present invention relates to ear seals for use in connection with ear cups employed in headsets, ear defenders or protectors, helmets and the like. The invention particularly relates to a circumaural seal that provides comfort, a high performance audio seal between the earcup and a user's head, and high damping.
The noise inside the crew compartments of military and some commercial ground vehicles, aircraft, and helicopters routinely exceeds normal safe exposure levels and can reach extreme noise levels of 115 dBA or more. Voice communications using typical microphones in combination with headsets and/or helmets equipped with standard earphones can be seriously compromised in such high noise environments. Investigations have revealed that noise affects the nervous system, causing, for example, weariness, lack of concentration, nervousness, and irritability. For complex operations, crew performance is often closely correlated to speech intelligibility. Thus, high noise levels can cause the crew's performance to degrade as well as cause hearing damage and jeopardize safety.
Various active noise reduction (ANR) systems are available that can decrease to some degree the level of noise reaching the user's ears. However, the successful functioning of these (ANR) systems is often highly dependent upon adequate passive protection, i.e. dependent upon the circumaural seal and semi-rigid earcup used in connection with the ANR system.
Current, state-of-the-art circumaural earcup audio seals, however, are generally not very effective in high and extreme noise environments. Often, the earcup-to-head audio seal (ear seal) for ANR headsets does not get the level of design attention it deserves based on the critical role it plays in the total performance of the headset system. The ear seal must perform two functions exceptionally well; (1) develop the best possible audio seal between the ear cup and user's head, and (2) provide a comfortable fit (especially if it is worn for long periods). While comfort is important, the wrong choice of ear seal configuration and material will significantly degrade total system performance. One well known manufacturer employs silicone gel filled ear seals that are relatively comfortable. However, these ear seals are generally either marginally better or the same as other commercial aviation style headsets for providing an adequate audio seal. Furthermore, some state-of-the-art ear cup/ear-seal configurations exacerbate low frequency noise transmissions passing through the earcup by developing a low frequency earphone resonance because there is insufficient damping provided by the circumaural seal.
The circumaural earcup/ear-seal interface with the human skull, i.e., the fit, can have a critical influence on passive attenuation performance. Commercial seals (e.g., closed cell sponge or silicone gel), while sometimes comfortable, typically perform poorly as a noise barrier. In addition, these commercial seals, particularly near the lower extremity, i.e., at the jaw-to-skull interface, often fail to provide a satisfactory noise seal. In the area between the jaw bone and the skull, behind the ear, an opening of as much as 5-10 mm diameter may form between the ear seal and the user's head. This small breech in seal integrity can lessen passive attenuation by as much as 10 dBA. The audio seal design for other commercial seals can have considerably worse seal integrity. An inferior passive ear-seal noise barrier can seriously degrade the total system performance of a headset, ear defender, helmet or the like in a high noise environment.